1. Field of the Invention
The present invention relates generally to a method of evaluating a feeling of a gear shifting operation in a manual transmission, and more particularly, to a method of evaluating quantitatively heaviness or smoothness of a shifting operation of a gear shifting lever provided to extend from a manual transmission for use in a vehicle.
2. Description of the Prior Art
As known conventionally, in a manual transmission provided with a gear shifting lever and used in a vehicle, an input shaft, a counter shaft disposed to be rotated by the input shaft and an output disposed in parallel with the counter shaft are contained, and a plurality of gear trains having different gear ratios respectively are arranged between the input shaft and the counter, and the counter shaft and the output shaft. The gear train between the input shaft and the counter shaft is operative to transmit the rotation of the input shaft to the counter shaft. Gears mounted on the output shaft to constitute partially the gear trains between the counter shaft and the output shaft are not fixed to the outer shaft but made rotatable freely at the outer shaft. When the gear shifting lever is manipulated, one of the gears mounted on the output shaft is caused to engage through a synchromesh device with the output shaft so that a speed corresponding to a gear ratio of the gear train which includes the gear engaged through synchromesh device with the output shaft is selected Further, in a condition where a particular speed is selected, the input shaft is engaged through another synchromesh device with the output shaft so that the rotation of the input shaft is transmitted directly to the output shaft.
The synchromesh device employed in the manual transmission comprises fundamentally a clutch hub engaged with the output shaft to be rotated thereby and provided thereon with external spline teeth, a synchronizing sleeve provided thereon internal spline teeth for engaging with the external spline teeth of the clutch hub, and a clutch gear incorporated with a gear to synchronize which is mounted to be rotatable freely on the output shaft or mounted fixedly on the input shaft and provided thereon with external spline teeth for engaging with the internal spline teeth of the synchronizing sleeve. In case of manipulation of the gear shifting lever, the synchronizing sleeve is moved along the output shaft to cause the internal spline teeth provided on the synchronizing sleeve to engage with both the external spline teeth provided on the clutch hub and the external spline teeth provided on the clutch gear, so that the rotation of the gear to synchronize is transmitted through the clutch gear, the synchronizing sleeve and clutch hub to the output shaft
In such a synchromesh device, it is required that the gear to synchronize be mounted to be rotatable freely on the output shaft or mounted fixedly on the input shaft is synchronized in rotation with the synchronizing sleeve which rotates together with the output shaft in order that the internal spline teeth provided on the synchronizing sleeve can be engaged smoothly with the external spline teeth provided on the clutch gear. Therefore, in general, the synchromesh device further comprises a synchronizer ring having external spline teeth for engaging with the internal spline teeth provided on the synchronizing sleeve is provided between the synchronizing sleeve and the clutch gear, and a chamfer is formed at an end of each of the internal spline teeth provided on the synchronizing sleeve, the external teeth provided on the synchronizer ring, and the external teeth provided on the clutch gear, so that the internal spline teeth can thrust through easily and engage with the external teeth provided on the synchronizer ring or the external teeth provided on the clutch gear.
In the synchromesh device having the synchronizer ring, when the gear shifting lever is manipulated, the synchronizing sleeve is moved to the clutch gear and key members accompanying with the synchronizing sleeve push the synchronizer ring to move the same toward the clutch gear. The synchronizer ring moved to the clutch gear engages with a conical portion projecting from the gear to synchronize toward the synchronizing sleeve, so that the gear to synchronize is put into synchronism in rotation with the synchronizing sleeve, clutch hub and output shaft by frictional force acting between the synchronizer ring and the conical portion Under a condition wherein the gear to synchronize is put into synchronism in rotation with the synchronizing sleeve, the internal spline teeth provided on the synchronizing sleeve thrust through the external spline teeth provided on the synchronizer ring to engage with the same. The synchronizing sleeve put into engagement with the synchronizer ring is further moved toward the clutch gear and the internal spline teeth provided on the synchronizing sleeve thrust through the external spline teeth provided on the clutch gear to engage with the same.
When the synchronizing operation is performed between the synchronizing sleeve and the clutch gear, the thrusting and engaging operation of the internal spline teeth provided on the synchronizing sleeve acting upon the external spline teeth provided on the synchronizer ring, and the thrusting and engaging operation of the internal spline teeth provided on the synchronizing sleeve acting upon the external spline teeth provided on the clutch gear are carried out successively as described above in the synchromesh device, load imposed on the gear shifting lever and moving speed of the gear shifting lever are varied with lapse of time Such variations in the load imposed on the gear shifting lever and in the moving speed of the gear shifting lever exert a great influence upon a feeling of a gear shifting operation in the manual transmission, that is, heaviness, smoothness and sensory factors of a shifting operation of the gear shifting lever.
In manufacturing of manual transmissions, a prototype of the transmission is subjected to a test for evaluating a feeling of a gear shifting operation for the purpose of designing a manual transmission with which an operator obtains a superior feeling of the gear shifting operation at a step for developing manual transmissions, and each of newly produced manual transmissions is subjected also to a test for evaluating the feeling of the gear shifting operation at, for example, a final stage of an assembly line for the purpose of supplying manual transmissions with each of which an operator obtains a superior feeling of the gear shifting operation at a step for producing manual transmissions. However, since the test for evaluating the feeling of the gear shifting operation relies conventionally upon sense of an operator who actually manipulates a gear shifting lever of the manual transmission, different results of evaluation may be derived from the same manual transmission by different operators, respectively.
Therefore, at the step for developing manual transmissions, it is required that a large number of tests for evaluating the feeling of the gear shifting operation are conducted repeatedly on prototypes assembled with different parts for finding out the most appropriate specification for each type of manual transmissions and this results disadvantageously in many man-hours and a large amount of expense. Further, at the step for producing manual transmissions, the test relying upon sense of an operator results in a problem that it is difficult to supply manual transmissions made uniform in quality.